What is a pure substance?

A pure substance is a form of matter that has a definite composition and distinct properties. It may consist of only one type of atoms (examples: Fe(s), N2(g), S8(s)), or of only one compound where the atoms are connected in a defined way, (examples: FeS(s), CH4(g), NaNO3(s), H2O(l)). Many substances called “pure” in everyday life like “Pure Honey”, “Pure Silk” etc. are not pure in a scientific sense but they are mixtures.